It has been suggested that environmental toxicants that trigger long-term alterations in the programming of 5HT function contribute to appetitive and affective disorders, and resulting increases in the incidence of obesity, diabetes, and depression (Slikker and Schwetz 2003; Toschke et al. 2002; von Kries et al. 2002). This evidence concerns the gene HTR5A and obesity due to melanocortin 4 receptor deficiency.